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Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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814 FXUS63 KDVN 110833 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 333 AM CDT Thu Jul 11 2024 .KEY MESSAGES... - Scattered showers and thunderstorms today, although low confidence in coverage and timing. Slow movement will bring risk of flash flooding with training storms. - Becoming very warm and humid this weekend and into next week, with heat indices in the upper 90s and low 100s. Heat headlines may eventually be needed Sunday and Monday. - Ring of fire pattern early next week may bring strong/severe thunderstorms close to the forecast area and relief from the heat. - Moderate to major river flooding continues on the Mississippi River with most sites crested or cresting in the coming days. && .SHORT TERM /THROUGH TONIGHT/... Issued at 320 AM CDT Thu Jul 11 2024 Scattered showers and isolated thunderstorms have been ongoing for much of the night north of I-80. This was due to the pivoting upper low overhead that was centered over Johnson county at 3am. Due to the slow movement of storms, some impressive rain amounts over 1.5" in 1 hr or 2" in 3 hrs based on spotters and radar estimates were reported. A flash flood warning was issued for northern portions of Linn and Benton counties early this AM for these totals. In addition to the storms, patchy areas of fog with visibilities under a mile have developed mainly south of I-80 where clouds have cleared. Some localized dense fog was also observed outside our office here at DVN. 00z models and CAMs have performed poorly this morning and have relied on nowcasting, particularly with storm placement. Early This Morning...areas of fog will continue to expand through 6am, with visibilities under a mile at times. Some localized dense fog may occur so motorists should use caution and use low beams if they encounter dense fog. Visibilities will quickly improve after 7am. Today...upper low to track across the area this morning, with additional showers and storms expected through the afternoon hours. The activity early this AM was occurring in the 700-500mb mean RH gradient per SPC Mesoanalysis. Based on this and the latest CAMs that have started to catch on to what actually is occurring, the highest coverage this afternoon would be in west central and north central IL and this is where chance PoPs were added. With high PWs still in the 1.3-1.5" range and slow storm motions under 15 mph, another quick 1-2" rain may occur in very narrow swaths. Some localized 3" amounts not out of the question as well. Rain rates between 0.75"-1.5"/hr can be expected in the strongest cells. Deep layer shear values less than 20 kts will preclude any severe potential, although NST values over 1 across west central IL may allow for funnels to occur this afternoon. Highs today were lowered some and will a degree or two cooler than yesterday, with highs topping out in the lower 80s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 320 AM CDT Thu Jul 11 2024 Friday...strong upper level ridge begins to dampen some across the western CONUS, but keeps us in northwest flow aloft. Depending on which model you look at, there will be several waves that top this ridge and move into the northern Great Plains. The 1st one of interest would arrive as early as Friday night if the 00z NAM is correct. Moisture will be lacking and have maintained a dry forecast for now on Friday. This Weekend...more upper level waves will move through the flow in a "ring of fire" like pattern. Models still in disagreement timing these waves and any associated impact (MCS track?) to the CWA. The 00z models keep the main wave well to our north across MN/WI on Sunday and thus a dry forecast for our area. However, building heat will be seen with 850mb temps rising into the 23-26C range. This will boost temps into the 90s and combined with dewpoints in the low 70s (perhaps even higher due to mature corn crop), will push afternoon heat indices into the upper 90s and low 100s, especially on Sunday. The warmest readings will be seen south of I-80 in the afternoon and a heat headline may be needed. Early Next Week...after another very warm and humid day Monday with possible heat headlines, a cold front will move through late Monday night into Tuesday. This will likely bring some strong storms to our area and relief from the heat. This will be something to monitor in later forecasts. Beyond Tuesday, temperatures will be cooler with highs only in the low to mid 80s. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1222 AM CDT Thu Jul 11 2024 A slow moving shortwave will rotate through the forecast area today, bringing additional chances of showers and thunderstorms. In the near term, this will be confined to areas north of I-80 and have included a TEMPO at CID for this possibility. South of I-80, fog will be a concern early this AM with Nighttime Microphysics channel already showing signs of development. Have not gone as low as some guidance suggested which was widespread LIFR cigs/vsbys, but went IFR for now and will continue to monitor trends this morning. Thunder potential this afternoon too low for mention at this time, but if it occurred the most likely terminals impacted would be MLI/BRL. && .HYDROLOGY... Issued at 124 PM CDT Mon Jul 8 2024 Precipitation in the next few days, especially in Iowa, is expected to be dry or very light. Thus, routed flow will continue on all of our rivers. The Mississippi River is currently cresting at major levels upstream of Camanche, IA, and near crest through Illinois City. The crest may take 1 to as much as 3 days to pass. From Le Claire to Burlington, the respective crests will commence within the next 1 to 2 days. Keokuk is now forecast to crest within Moderate Flood category beginning Friday. Gregory Landing is forecast to remain near 19.5 feet through the week. Tributary Rivers: The Cedar River at Cedar Rapids crested below flood stage and will fall over the next several days. On the Cedar River at Conesville, minor flooding will continue. It will see a secondary crest near 14.4 feet Wednesday night into Thursday. The Wapsipinicon River at Dewitt is forecast to remain in moderate flooding category through late on Friday. The Iowa River at Oakville is seeing high water levels due to backwater affects from the Mississippi River. It is forecast to remain near 11.4 or 11.5 feet through midweek and then rise to near 12.1 feet late Thursday into Friday. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Gross LONG TERM...Gross AVIATION...Gross HYDROLOGY...Gunkel